Electric-erosion machine for dimensional working of current conducting materials in a liquid medium



June 23, 1964 A. L. LIVSHITS ETAL ELECTRIC-EROSION MACHINE FOR DIMENSIONAL WORKING OF CURRENT Filed May 19. 1961 CONDUCTING MATERIALS IN A LIQUID MEDIUM 9 Sheets-Sheet 1 F [V vex/foes A 7. Ken V6725 In A/. 6'04 0 v0 4/ D. F. )44KH/M0 way A/. I. .54 n3 rE/A/ ATTORNEYJ Ju 23, 1964 A. LIVSHITS ETAL 3,138,691

ELECTRIC-EROSION MACHINE FOR DIMENSIONAL WORKING OF CURRENT CONDUCTING MATERIALS IN A LIQUID MEDIUM 9 Sheets-Sheet 2 Filed May 19, 1961 Z V H wm x m sxwflvm e v 5 A L 0 I 6 0 1 TZEMOOKU -1 sm fi z? N M45 f 0 ATTORNEYS June 1964 A. L. LIVSHITS ETAL 3,138, 9

ELEcTR1cERos1oN MACHINE FOR DIMENSIONAL WORKING OF CURRENT CONDUCTING MATERIALS IN A LIQUID MEDIUM Filed May 19, 1961 9 Sheets-Sheet 3 BY M ATTORNEY5 3,138,691 ING OF CURRENT June 1964 A. L. LIVSHITS ETAL ELECTRIC-EROSION MACHINE FOR DIMENSIONAL WORK CONDUCTING MATERIALS IN A LIQUID MEDIUM 9 Sheets-Sheet 4 Filed May 19, 1961 f/vl/E/v Toe s r ,4. A. L/vs/w 7-5 M. [.ZQ/SKMHM A. 7. Kev; V5715 5. 6'. P01); 420v M M 6040 vov D. F. Y4KH/Mov/cH ATTORNEYJ June 23, 1964 A. L. LIVSHITS ETAL ELECTRIC-EROSION MACHINE FOR DIMENSIONAL. WORKING OF CURRENT CONDUCTING MATERIALS IN A LIQUID MEDIUM 9 Sheets-Sheet 5 Filed May 19, 1961 Z U ,y M n/M &/ fl 7 ATTORNEKY June 23, 1964 ELECTRIC-EROSION MAc'HIN CONDUCTING MA Filed May 19, 1961 9 Sheets-Sheet 6 f/Vl/E'A/ Toes BY fJW ATTORNEYS m 1964 A. LIVSHITS ETAL 3,138,691

ELECTRIC-EROSION MACHINE FOR DIMENSIONAL WORKING OF CURRENT CONDUCTING MATERIALS IN A LIQUID MEDIUM Filed May l9. 1961 9 Sheets-Sheet 7 ATTORNEYS n 1964 A. L. LIVSHITS ETAL 3,133,691

ELECTRIC-EROSION MACHINE FOR DIMENSIONAL WORKING OF CURRENT CQNDUCTING MATERIALS IN A LIQUID MEDIUM Filed May 19, 1961 9 Sheets-Sheet 8 H m M W W 53720;. n e w fl ma A 3 $35 2 WM?? M/3 2m 3,138,691 G OF CURRENT UM 9 Sheets-Sheet 9 June 1964 A. LIVSHITS ETAL ELECTRIC-EROSION MACHINE FOR DIMENSIONAL WORKIN CONDUCTING MATERIALS IN A LIQUID MEDI Filed May 19, 1961 United States Patent C) ice 3,138,691 ELECTRIC-EROSION MACHINE FOR DIMENSION- AL WORKING OF CURRENT CONDUCTING MATERIALS IN A LIQUID MEDIUM Abram Lazarevich Livshits, Michail Iosifovich Briskman, Arkady Timofeievich Kravets, Serguei 'Sergueievrch Podlazov, Valery Nickolaievich Solovov, Dmitry Fedorovich Yakhimovicll, and N'aum Isaakovich Blitstein,

all of Moscow, U.S.S.R.

Filed May 19, 1961, Ser. No. 111,331 6 Claims. (Cl. 21969) The present invention relates to an electrical erosion machine for dimensional machining of current-conducting materials in a liquid medium.

Existing types of electric erosion machines used for metal working have the following inherent limitations: relatively low production capacity, considerable Wear of electrode-tool, and insuflicient constructional rigidity for machining heavy parts with required accuracy.

This proposed electric erosion machine is free of the mentioned shortcomings and has, in comparison with known types, the following advantages:

(a) greater production capacity due to higher working speeds;

(b) less wear of the tool;

universal application, adequate rigidity and means for handling bulky and heavy parts;

(d) a tank designed for rapidly bringing any work piece into and out of the machine working zone;

(e) automatic working cycle.

A kinematic diagram of the machine is shown in FIG. 1, while FIG. 2 is a similar view along arrow A. FIG. 3 presents a sectional view of the machine table and tank; FIG. 4 is an elevational view of the tool head, and FIGS. 5 and 6 are sectional views taken on lines II and IIII of FIG. 4; FIG. 7 is a sectional view showing the tool vertical motion counter; FIG. 8 is a diagram of the automatic feed regulator; FIG. 9 is a diagram of the arrangement for delivering the control signal in connection with several parallel circuits having a common source of supply; FIG. 10 is a similar diagram for circuits with individual supply; FIG. 11 is an alternative diagram of the automatic feed regulator, and FIGS. 12 and 13 show an alternative form of the machine head.

The machine head can be shifted, with respect to the table, in a horizontal plane with two degrees of freedom and, also, has a vertical motion that can be combined with the rotation of the tool and its vertical oscillations. The crosspiece can be moved manually by means of handwheel 1 (see FIG. 1), or driven by electric motor 2 with which it is engaged by two pairs of cylindrical gear wheels 3 and 4, screw pair 5 and guide screw 6 (see FIG. 2).

The head is moved along the crosspiece by means of handwheel 7 through a pair of bevel gear wheels 8 and screw 9.

Vertical feed of the tool is provided by an automatic feed regulator coupled with electric motor 10 by means of worm and planetary gears 11 and 12, cylindrical gear wheels 13 and tool vertical feed screw 14.

.A rapid adjusting motion is provided by an individual electric motor 15 through worm and bevel gears 16 and 17, cylindrical gear wheels 13 and screw 14. The planetary gear allows simultaneous, or separate operation of either of the motor drives. Manual vertical displacement is brought about by handwheel 18 through two pairs of bevel and three pairs of cylindrical gear wheels. When manual operation is required, clutches 20' and 21 are shifted to the left as viewed in FIG. 1 together with shaft 22 by turning handle 19, and are shifted to the right by the same handle if the motor drive is used.

3,138,691 Patented June 23, 1964 The vertical motion of the head is counted off by means of rack-and-piirion gear 23, electromagnetic clutch 24 and counting mechanism 25. The adjusting rotary motion of the head is brought about by handwheel 26 and worm gear 27.

The machine tank is lifted and lowered by means of electric motor 28, a pair of cylindrical gearwheels 29 and two worm pairs 30 and, also, two rack-and-pinion gears 31, the racks of which are attached to rods supporting the tank.

Table 32 (see FIG. 3) comprises a rigid stand 33 and base plate 34 with special slots for securing the work piece in place. The latter may be fixed in place by other means, such as a magnetic bed plate.

Double-walled vertically movable tank 35 is furnished with packing 36 of wear-resistant material.

During machine operation, the liquid is continuously supplied to the tank through openings 37 of the table by pump 38. The surplus liquid overflows through openings 39 into the passage between the walls of the tank. Continuous circulation of the liquid improves its cooling. Spraying and ignition of the liquid due to a low levelof the liquid in the tank is avoided by means of relay 40 which prevents operation of the machine with an insufficient quantity of the liquid in the tank.

The table of the machine has slantings for speeding up the drain of liquid when the tank packing is lowered beneath a certain level. The tank is fixed to two rods 41 provided with racks for lowering and lifting the tank.

The tool head serves for feeding the tool and can be given a vertical oscillatory motion (vibration).

' Spindle 42 within the head shell (see FIG. 4) is supported by two flat springs 43 and 44 that allow tool movement in a vertical direction and provide extra stiifness in all other directions. The oscillatory motion is imparted to the spindle by electromagnet 45, the core 'of which is attached to the spindle. The lower part 'of the spindle accommodates built-in worm gear 47 (see FIG. 5) for turning the tool. The shell of the head travels along vertical cylindrical guides 48 (see FIG. 6) of carriage 49 on rollers 50 mounted on roller bearings.

A protective arrangement with flexible strips 51 is mounted on the top and bottom of the head for protecting the guide rollers from dust and dirt.

The tool is moved in a vertical direction by screw 52 which is rotated by a normal and high-speed feed drive through self-adjusting nut 53. The screw is driven through reduction gear 54. The spindle travel is limited by limit switches 55 and 56 and stop 57.

The tool vertical travel counting mechanism is actuated by a rack-and-pinion gear. The counter device is operated by shaft 58 (see FIG. 7) which is coupled with it by means of electromagnetic clutch 59 and friction mechanism 60.

Dial 61 serves for setting the tool travel and dial 62 for reading the tool travel. The travel is counted off starting from the moment that the tool touches the work. At this moment, switch 63 energizes electromagnetic clutch 59 and the rotary motion of the shaft 58 drives pointer 64. One revolution of this pointer corresponds to a travel of 100 mm., and one revolution of pointer 65 corresponds to a travel of 10 mm. Stop 66 actuates the feed limiting switch 67 after the set distance has been covered.

The machine can also be used with a self-contained tool head designed for operation at an angle outside the machine, or can be equipped with several tool heads (see FIGS. 12 and 13).

The head slide 68 moving along ball guides 69 in the head shell 70 is actuated by electric motor 71 through worm reduction gear and guide screw 72.

The slide houses vibrator spindle 73 that is furnished with chuck 74 for receiving and securing the tool.

Ball guides 75 are employed for ensuring a high-precision travel of the vibrator spindle. The spacing of guides 75 is set by means of screw 76 and lever 77.

Diaphragm 78 serves as a spring and, also, prevents the penetration of dirt.

The oscillatory motion is provided by electromagnet 79. The bottom of shell '70 is encircled by cup 80 with lining 81. The cup can be moved in a vertical direction and is keyed to the shell by the nut 82. This serves to provide a closed cavity around the working zone required for operation outside the tank, or in cases when the head is tilted.

The liquid is supplied by the pump into the vibrator spindle cavity through an inlet nipple and is passed on to the working zone through a hole in the tool. The liquid is let out of the cup through outlet nipple 83.

Limit switch 84 limits the downward travel of the slide.

Handle 85 provides for manual operation of the slide, and coupling 86 serves to disengage the worm gear drive during this operation.

Tongue 87 serves for fastening the head.

The gap between the tool and part being worked is regulated by means of a special automatic regulator. The circuit diagram of the regulator shown in FIG. 8 has two stages of amplification. The first stage employs semiconductor triodes (transistors) and the second-magnetic amplifiers.

The control signal is delivered from the erosion gap that is supplied by an impulse generator. The magnitude of the control signal is regulated by potentiometer R After having been amplified by the semiconductor (transistor) amplifier, the control signal is supplied to the control windings 1MV6, 2MV6 (1MV7, 2MV7) of the differential magnetic amplifier. The second stage of the amplifier circuit is of a twin full-wave bridge type. Each section is supplied by an individual winding of transformer Tp. The amplification factor is improved by internal positive feedback of the differential magnetic amplifier. This is accomplished by connecting the germaniurn diodes in-series with each A.C. winding.

The sensitivity and accuracy of duty maintenance is improved by the introduction of a negative voltage feedback that operates only during downward travel of the tool. This is attained by supplying the motor armature voltage to triodes 1T and 2T through valve D. OB designates the field winding of the actuating motor M.

In cases when the part, or parts being machined is simultaneously machined by several tools having individual sources of supply (multicircuit working), the control signal is delivered to the automatic regulator from the circuit'carrying the greatest load.

In the circuit with a common generator MGI and current-limiting resistors R R (see FIG. 9), the control signal is supplied from resistor r, connected in-parallel with resistors R R through valves D D The voltage drop across this resistor is equal to the voltage drop across the circuit carrying the greatest load. The control signals of circuits carrying lesser loads do not enter the control signal circuit due to an opposed direction of the voltage drop across resistor r The control signal is compared with the voltage delivered by potentiometer r and is supplied from resistor r to the input of the amplifier (a-b). Choke coil D and capacitor C form a filter.

In cases when the circuits are supplied by different generators lMGI and ZMGI (see FIG. 10), resistor r is connected in parallel to resistors R R through valves D -D and B B that form a common point of this connection.

Capacitor C is included in cases when the generators operate at various phases in order to be able to compare lagging and leading signals.

The automatic regulator is made to operate at optimal duty conditions by applying the control signal to two selectors and a correcting device. The first selector limits the magnitude of the signal and, thus, eliminates the influence of increasing generator voltage. The second selector records unused, or partly used voltage impulses. The correcting device records voltage impulses of lesser magnitude than operating impulses, or the absence of impulses (short-circuit conditions).

The minimum selector and correcting device control the operation of the arms of the balance amplifier. The power amplifier and actuating motor are connected to the output of this amplifier and, consequently, the tool is fed forward when idle impulses are recorded, and

1 is drawn back when there are short-circuit impulses.

As a result, the tool feed is independant of existing duty conditions and the area of the work.

An example of this regulator is shown in FIG. 11.

Valve D and resistor R are connected across the input, the voltage drop across R being opposed to that of the valve. In cases when the signal delivered from the erosion gap exceeds in value the opposed voltage, valve D conducts current and circuit D R shunts the input. As a result, the impulses applied to grid L do not exceed a pre-determined value. This assures that the operation of the regulating system is not influenced by upper variations of the impulse generator MGI voltage (maxi mum limit).

Under normal conditions, the left half of valve L is shut off by a negative bias. The magnitude of this bias is selected so to open the valve at a control signal exceeding normal value (minimum limit).

The signal is supplied from resistor R of the cathode circuit of valve L to the right half of valve L Winding 0V1 of rotary amplifier EMV supplying actuating motor M is connected to the anode circuit of valve L At a flow of current through winding 0V1, the motor feeds the tool.

A signal shutting off the right half of valve L is supplied from the same resistor through transformer Tp and rectifier B. The left half of valve L is, correspondingy, shut off, as a negative signal is supplied to the grid of this valve from resistor R When there are no impulses (at short-circuit conditions), the left half of valve L and the right half of valve L are shut off, but the right half of valve L is opened (as no negative signal is applied to the grid), and the left half of valve L (to the anode circuit of which the rotary amplifier winding 0V2 is connected) is likewise opened.

At a flow of current through winding 0V2 the tool is drawn back.

Windings 0V3 and 0V4 are used for producing a negative feedback according to the speed of the motor.

Relay P serves for switching the electric motor for high-rate withdrawal of the tool.

We claim:

1. Apparatus for machining metal work pieces in a liquid medium by electric erosion, said apparatus comprising a base, a Work table mounted on said base, liquid containing means operatively associated with said table for receiving work pieces, an arm slidably mounted on said base for horizontal movement with respect to said table and overhanging said table, selectively operable manual and power operated means for moving said arm, a tool head slidably mounted on said arm above said table for horizontal movement at right angles to the movement of said arm, manual means for moving said head, a vertically movable casing carried by said 'head, selectively operable manual and power operated means, including two motors for moving said casing vertically, a magnetically operable vertically vibrating electrode holding spindle carried by said casing, an electrode mounted on said spindle, one of said motors driving said casing through a planetary reduction gear and the other motor driving said casing through spur gearing, means for regulating the movement of said casing comprising a regulator including a two-stage amplifier, one

of said stages using semi-conductor triodes and the other stage using differential magnetic amplifiers, the second stage of the amplifier being of the twin, full Wave bridge type with feedback and an impulse generator for energizing said electrode with a negative voltage of a pre determined duration and frequency.

2. Apparatus as defined in claim 1, in which the operation of said regulator is controlled by a control signal provided from said electrode through electronic valves and two electronic selectors to the regulator.

3. Apparatus as defined in claim 1, in which means is provided for rendering said apparatus inoperative when the liquid level in said liquid containing means is below a predetermined point.

4. Apparatus as defined in claim 1, including an auxiliary tool head removably carried by said spindle, an electrode holding spindle in said auxiliary head, separate variable speed means for moving said last named spindle vertically and means for providing vertical vibration of said last named spindle.

5. Apparatus as defined in claim 1, including direct reading dial means for indicating the vertical movement of said electrode and magnetic clutch means for coupling said dial means to said tool head.

6. Apparatus for machining metal work pieces in a liquid medium by electric erosion, said apparatus comprising a base, a work table mounted on said base for supporting a work piece, an arm slidably mounted on said base for horizontal movement with respect to said table and overhanging said table, selectively operable manual and power operated means for moving said arm,

a tool head slidably mounted on said arm above said table for horizontal movement at right angles to the movement of said arm, manual means for moving said head, a vertically movable casing carried by said head and having a downwardly opening recess for receiving a Work piece, packing means for providing a liquid-tight joint between a work piece and said casing, means to circulate liquid through said recess, selectively operable manual and power operated means including two motors for moving said casing vertically, a magnetically operable vertically vibrating electrode holding spindle carried by said casing, an electrode mounted on said spindle and terminating within said recess, one of said motors driving said casing through a planetary reduction gear and the other motor driving said casing through spur gearing, means for regulating the movement of said casing comprising a regulator including a two-stage amplifier, one of said stages using semi-conductor triodes and the other stage using differential magnetic amplifiers, the second stage of the amplifier being of the twin, full wave bridge type with feedback and an impulse generator for energizing said electrode with a negative voltage of a predetermined duration and frequency.

References Cited in the file of this patent UNITED STATES PATENTS 2,766,364 Higgins et al Oct. 9, 1956 2,773,968 Martellotti et al. Dec. 11, 1956 2,908,797 Stegler Oct. 13, 1959 2,981,822 Larkins Apr. 25, 1961 

1. APPARATUS FOR MACHINING METAL WORK PIECES IN A LIQUID MEDIUM BY ELECTRIC EROSION, SAID APPARATUS COMPRISING A BASE, A WORK TABLE MOUNTED ON SAID BASE, LIQUID CONTAINING MEANS OPERATIVELY ASSOCIATED WITH SAID TABLE FOR RECEIVING WORK PIECES, AN ARM SLIDABLY MOUNTED ON SAID BASE FOR HORIZONTAL MOVEMENT WITH RESPECT TO SAID TABLE AND OVERHANGING SAID TABLE, SELECTIVELY OPERAABLE MANUAL AND POWER OPERATED MEANS FOR MOVING SAID ARM, A TOOL HEAD SLIDABLY MOUNTED ON SAID ARM ABOVE SAID TABLE FOR HORIZONTAL MOVEMENT AT RIGHT ANGLES TO THE MOVEMENT OF SAID ARM, MANUAL MEANS FOR MOVING SAID HEAD, A VERTICALLY MOVABLE CASING CARRIED BY SAID HEAD, SELECTIVELY OPERABLE MANUAL AND POWER OPERATED MEANS, INCLUDING TWO MOTORS FOR MOVING SAID CASING VERTICALLY, A MAGNETICALLY OPERABLE VERTICALLY VIBRATING ELECTRODE HOLDING SPINDLE CARRIED BY SAID CASING, AN ELECTRODE MOUNTED ON SAID SPINDLE, ONE OF SAID MOTORS DRIVING SAID CASING THROUGH A PLANETARY REDUCTION GEAR AND THE OTHER MOTOR DRIVING SAID CASING THROUGH SPUR GEARING, MEANS FOR REGULATING THE MOVEMENT OF SAID CASING COMPRISING A REGULATOR INCLUDING A TWO-STAGE AMPLIFIER, ONE OF SAID STAGES USING SEMI-CONDUCTOR TRIODES AND THE OTHER STAGE USING DIFFERENTIAL MAGNETIC AMPLIFIERS, THE SECOND STAGE OF THE AMPLIFIER BEING OF THE TWIN, FULL WAVE BRIDGE TYPE WITH FEEDBACK AND AN IMPULSE GENERATOR FOR ENERGIZING SAID ELECTRODE WITH A NEGATIVE VOLTAGE OF A PREDETERMINED DURATION AND FREQUENCY. 